1. Field of the Invention
The present invention generally relates to a nitride semiconductor structure, in particular to a nitride semiconductor structure having improved work efficiency.
2. Description of Related Art
Light-emitting diode (LED) is a nitride semiconductor structure formed from compound containing semiconductor materials of elements in III-V group, such as gallium nitride, gallium phosphide and gallium arsenide. The LED in use has life time up to 100,000 hours and has advantages of fast response speed (about 10−9 seconds), small volume, saving power, low contamination, high reliability and easy for massive production, and so on. Therefore, the LED has been used a lot in various applications, such as illuminating apparatus, traffic sign, cellular phone, scanner and fax machine
However, generally in the fabrication process for the nitride semiconductor structure, a lattice dislocation may easily occur during epitaxy process of semiconductor due to the difference about the lattice constant and the thermal expansion coefficient (CTE) between the semiconductor layer and the substrate. Further, an issue of thermal stress can also occur due to mismatch of the thermal expansion coefficient (CTE). The nitride semiconductor structure suffers the stress and gets serious bending, which increases the possibility for the occurrence of crack and influences work efficiency.